The privatisation of forensic testing in Britain is leading to catastrophic failures and potential miscarriages of justice, the pioneer of mass DNA profiling has warned.

In a damning indictment of the new system of forensic testing, Professor Peter Gill said the "wheels were already falling off" following the switch to private providers and police labs from the loss-making Forensic Science Service (FSS), which closed its doors for the last time at the weekend. He has called for thousands of criminal cases to be reviewed following high-profile blunders by the country's biggest private testing centre, LGC. The mistakes have also led to calls for a public inquiry.

The FSS, which carried out 60 per cent of forensic work in Britain when the Government announced its closure in December 2010, finally shut down at the weekend with only its archives retained for historic reviews. The Government blamed monthly £2m losses but its closure leaves Britain as the only major country without a national forensics service. Professor Gill, who co-wrote the first scientific paper on uses of DNA for forensic science and led the work which set up the national database, quit the FSS in 2008 in protest at the agency's increasing commercialisation.

Professor Gill and other critics claim the changes over the past decade led to:

* the loss of niche technical skills including fibre analysis;

* forensic material from the same crime split between different providers;

* the end of expensive, ground-breaking research that contributed to some remarkable breakthroughs;

* the outsourcing of cases because private companies cannot cope with the surge in cases.

The LGC errors included the contamination between two samples in a lab. In one rape case it led to a false finding linking an innocent man to the crime scene. It was revealed last week the company also accidentally created a non-existent suspect during the inquiry into Gareth Williams, the MI6 worker whose body was found inside a bag at his London flat – leading police up a blind alley for more than a year.

The forensic science regulator said it had checked 26,000 samples after the rape-case error and said it found no other problems. But Professor Gill expressed doubt over the inquiry's findings.

"The only way forward is for the courts individually to reconsider the affected cases via the appeal procedure... otherwise it seems to me that there is a significant possibility of miscarriage of justice in the cases that comprise the affected batch of samples," he said.

"I'm surprised that the wheels are falling off so quickly. I didn't think we'd hear anything for two years – not a couple of weeks. You can be absolutely certain this is not being picked up in all cases. It's just the tip of the iceberg."

Professor Gill's criticisms followed a survey in February in the New Scientist magazine which found that 75 per cent of forensic scientists who responded believed that miscarriages of justice were more likely under the new system.

Alastair Logan, the solicitor who represented the Guildford Four and Maguire Seven, said the Government would be forced to restart a state-run forensic service "in 10 to 15 years when the miscarriages of justice start to happen".

A Home Office spokeswoman said: "The Forensic Science Service was making huge losses. The wind-down of the FSS has ensured the police and the criminal-justice system continue to have the forensics capability they need to bring criminals to justice."

LGC said it took on a temporary staff for a short period during the transfer of work from FSS. "LGC manages all aspects of cases that are sent to us," it said.

DNA testing: landmark cases

Colin Pitchfork

In 1987, Pitchfork was the first person in Britain to be convicted of murder based on DNA identification, developed two years earlier by Alec Jeffreys, a professor of genetics at Leicester University. The case involved the rape and murder of two girls in Leicestershire in the 1980s. The DNA evidence also cleared a man previously convicted for the killings. The screening of 5,000 men failed to obtain a match with semen found at the scene, but Pitchfork was finally arrested after a man boasted that he had been paid to give a semen sample on his behalf. Pitchfork was jailed for life.

Craig Harman

Harman was the first person in the world prosecuted using "familial" testing developed by the FSS. He killed a lorry driver by throwing a brick through the windscreen from a motorway footbridge. Using a partial DNA trace from the brick, the national DNA database was trawled to find anyone with similar DNA, i.e., a relative. This led to Harman, who admitted manslaughter in 2004 and was jailed for six years.